Yaaf.FSharp.Scripting

Documentation

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NuGet

Include as source file

Paket

You can include the functionality directly into your application by using paket source files:

paket.dependencies:

github matthid/Yaaf.FSharp.Scripting src/source/Yaaf.FSharp.Scripting/YaafFSharpScripting.fs

paket.references:

File: YaafFSharpScripting.fs

See http://fsprojects.github.io/Paket/github-dependencies.html for details.

NuGet

The YaafFSharpScripting.fs source code file is included in the nuget package as well. You can find it in content/YaafFSharpScripting.fs. By adding the source code file (as reference) to your project you don't need to add a nuget dependency (Yaaf.FSharp.Scripting) to your final package.

Quick intro

This library tries to improve the scripting capabilities of FSharp.

It builds on top of FSharp.Compiler.Service but provides a nice an clean API:

open Yaaf.FSharp.Scripting
use fsiSession = ScriptHost.CreateNew()
fsiSession.Reference (@"C:\MyAssembly.dll")
fsiSession.Open ("MyAssembly")

// hook 25 into the session with name test (ie "let test = 25")
// this works with any object
fsiSession.Let "test" 25

// Get a value out of the evaluator
let v = fsiSession.EvalExpression<int> "test"
assert (v = 25)

// Try to get a value (with handling error cases)
match fsiSession.Handle<int> fsiSession.EvalExpression "test" with
| InvalidExpressionType e -> 
  // not of type int
  // e.Value contains the result object, e.ExpectedType the expected type (int in this case)
  ()
| InvalidCode e -> 
  // couldn't get app value (compiler error, not defined or exception in the running code)
  // e.Input is the given text, e.Result is the compiler or the script output
  // Note: script exceptions are written as strings within e.Result
  ()
| Result r -> 
  // r is the value.
  ()

// Get the output of the snippet
let v = fsiSession.EvalInteractionWithOutput """printf "test" """
assert (v.Output.ScriptOutput = "test")

// Get the error message of the compilation
try fsiSession.EvalInteraction """ Some_Invalid_F# """
with :? FsiEvaluationException ev ->
    printfn "FSI said: %s" ev.Result.Error.FsiOutput
    printfn "Complete Error: %O" ev

// Load scripts
fsiSession.EvalScript "Script.fsx"

The library also provides some nice members which are missing in FSharp.Compiler.Service:

open Yaaf.FSharp.Scripting
open FSharp.Compiler.SourceCodeServices

// A Assembly -> FSharpEntity mapping (extension) function
let fsAssembly = FSharpAssembly.FromAssembly typeof<MyType>.Assembly

// A extension method to find the entity type
let fsType = fsAssembly.Value.FindType typeof<MyType>

And some extensions for System.Type to get the FSharp type name

// with concrete types.
let def = typeof<option<int>>
test <@ def.Name = "FSharpOption`1" @>
test <@ def.Namespace = "Microsoft.FSharp.Core" @>

test <@ def.FSharpParamList = "<System.Int32>" @>
test <@ def.FSharpFullName = "Microsoft.FSharp.Core.Option" @>
test <@ def.FSharpFullNameWithTypeArgs = "Microsoft.FSharp.Core.Option<System.Int32>" @>
test <@ def.FSharpName = "Option" @>

// With typedefs.
let def = typedefof<option<int>>
test <@ def.Name = "FSharpOption`1" @>
test <@ def.FullName = "Microsoft.FSharp.Core.FSharpOption`1" @>

test <@ def.FSharpParamList = "<_>" @>
test <@ def.FSharpFullName = "Microsoft.FSharp.Core.Option" @>
test <@ def.FSharpFullNameWithTypeArgs = "Microsoft.FSharp.Core.Option<_>" @>
test <@ def.FSharpName = "Option" @>